Wide QRS Tachycardia with Two P Wave Morphologies: What Is the Mechanism?

Abstract

A 38 years old male complained of occasional palpitation and came to our hospital for help. Twelve-lead electrocardiogram during the palpitation revealed a wide QRS tachycardia with two different P wave morphologies. Two different atrial activation sequences were found in the intracardiac recordings and they were comparable to the two different P wave morphologies from the surface ECG recordings. The first type of atrial activation pattern was retrograde concentric VA conduction with the earliest atrial activation at the proximal coronary sinus which created a negative polarity of P wave in the lead II of ECG. The second type of atrial activation pattern was conducted from the right atrium to the coronary sinus which was considered to be a normal sinus impulse and created a positive polarity of P wave in the lead II of ECG. The idiopathic left ventricular tachycardia was diagnosed by atrioventricular dissociation and the short His-ventricular interval. The catheter ablation was performed during tachycardia. The site of catheter ablation was located at the distal septum of the left ventricle where the characteristic double diastolic potentials as previous studies demonstrated was recorded. The tachycardia was terminated after one pulse of ablation. No further tachycardia could be induced after the ablation even under isoproterenol infusion.